The present disclosure generally relates to a load shedding system. More specifically, the present disclosure relates to a load shedding system for selectively shedding the load applied to a standby generator.
When there is a power outage, backup power may be provided by a standby generator. In some cases, the standby generator is started automatically after detection of the power outage. A standby generator that is started automatically usually requires an automatic transfer switch to connect electrical loads to the generator rather than from the power supply. A combination of a standby generator and an automatic transfer switch is generally installed by trained personnel.
Since the power supply by the standby generator is limited by the size of the generator, the amperage rating of the generator can limit the types of and number of appliances that are connected to the standby generator during power outages. As an example, large appliances such as air conditioners, hot water heaters and on-demand appliances such as microwave ovens and toasters can draw a significant amount of power that in combination may exceed the rating limit for the standby generator.
Presently, automatic transfer switches are available that include a series of priority circuits that allow the automatic transfer switch to selectively reduce the load on the generator when the load approaches the rated limit for the generator. Typically, the priority circuits are assigned a value from 1 to a maximum number, such as 6 or 8, where the circuit assigned priority value 1 has the highest priority. When the load on the generator approaches the rating for the generator, the automatic transfer switch begins to shed load by opening switches or relays to disconnect the load connected to the lowest priority circuit. The automatic transfer switch continues to shed the loads from the lowest priority circuit to the highest priority circuit until the load reaches a preset limit to ensure that the generator can continue to provide power to the highest priority loads connected to the generator. When the load on the generator is reduced, load shedding ceases.
During initial installation of the standby generator and automatic transfer switch, installers connect dedicated loads to each of the priority circuits based upon a perceived importance of each of the loads. As an example, an air conditioner may be connected to priority circuit 1 where a less important load, such as a pool pump, may be connected to priority circuit 3. Thus, when the total load on the generator nears the rating for the generator, the pool pump connected to priority circuit 3 is shed before the air conditioner connected to priority circuit 1.
As described above, the priority circuits in currently available automatic transfer switches are hardwire connected at the time of installation. Therefore, if a user desires to change the device connected to priority circuit 1, the electrical wiring to the transfer switch must be adjusted.